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1
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3answers
64 views

Would it be possible to pull Mars and Earth closer each other?

The burden of travelling between Mars and Earth comes from the distance. If the planets were closer, life could spread to Mars more easily, ensuring the survival of the intelligent lifeforms. What ...
4
votes
2answers
34 views

How would I find the velocity of an object after it doesn't fully enter the gravitational pull of a planet and is kind sling shot out of its gravity?

Obviously that question doesn't have a lot of jargon having to do with math and physics. I am not a physicist, I'm not a mathematician, I'm trying to make a game and simulate some physics found in ...
3
votes
2answers
103 views

What kind of effect would cosmic expansion have on planetary motion or keplerian orbit? [duplicate]

The question is, if two following phenomena are thought to effect to the motion of the planet that orbits a star: Celestial body is pulled by some massive star by ordinary Newtonian gravity: $$ m \...
1
vote
2answers
80 views

Why does Goldstein's derivation of orbits from Newton's law not yield the orbit consisting of symmetric oscillation along a line thru center of Sun?

Why does Goldstein's derivation of Keplerian orbits from Newton's law of gravity not yield the orbit consisting of symmetric oscillation along a line passing thru the center of the Sun? The fact that ...
-2
votes
0answers
42 views

Satellite collides with earth [duplicate]

Suppose we have a satellite in a circular orbit around the earth. We know that the velocity is given by $$v = \sqrt{\frac{GM}{r}}$$ I'm curious as to what conditions on a velocity change would require ...
1
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3answers
60 views

How to calculate transit time for a specific section of an orbit?

I've searched high and low and I haven't been able to find a formula for this. I'm trying to calculate the time it will take to transit through a defined arc length of an elliptical orbit, whose ...
3
votes
0answers
156 views

Travel time in elliptical orbit around the sun [closed]

Hi I'm calculating a problem, and I think it ought to be correct - but the result I get isn't. The problem is described as follow: A spacecraft is traveling from Earth to Venus in an elliptical, ...
-1
votes
2answers
39 views

Total Linear Momentum Conserved for Earth-Sun System? [closed]

According to 'Introductory Astronomy and Astrophysics' by Smith and Jacobs the total linear momentum of an isolated system is constant which they choose as zero, so they get (mv)1 = (mv)2. When I ...
43
votes
4answers
3k views

How far ahead can we predict solar and lunar eclipses?

The solar system is non-integrable and has chaos. The sun-earth-moon three-body system might be chaotic. So, how far into the future can we predict solar eclipses and/or lunar eclipses? How about ...
3
votes
1answer
64 views

How can an asteroid fall to a planet?

According to the Kepler's first law, the orbit of an asteroid would be an ellipse having the planet at one of the focuses (to a good approximation). Then how come can it ever fall to the planet?
46
votes
5answers
7k views

What does the Moon's orbit around the Sun look like?

I'm curious as to what the Moon's orbit around the Sun looks like. If there's an answer, what's the intuition for it? Here are some things I'm assuming when trying to tackle this question: The Moon'...
3
votes
3answers
186 views

Gravitational Null Point between Earth and Moon

I need help finding the gravitational null point point between the Earth and the Moon, the point beyond which you start falling towards Moon. I am having difficulty in taking into account the orbiting ...
9
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3answers
3k views

Why is Larry Niven's Ringworld Unstable?

In his 1970 science fiction novel Ringworld, author Larry Niven describes the eponymous Ringworld, a gigantic structure shaped as a ring with a radius of around 1 AU, rotating around a star in the ...
1
vote
1answer
318 views

Determing Velocity of Moons

I have a question that I believe is relatively easy to answer, I am working on an $N$-body simulation of a fictional star system and am having trouble finding the velocity of moons so that they will ...
3
votes
2answers
66 views

How deep does a gravity well need to be to remove particles from a planetary body?

I almost considered asking this question on WorldBuilding, however I wanted the brute mathematics on the subject, so please excuse the theoretical nature of this question. I understand the basic ...
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votes
3answers
97 views

Gravity effects when deleting stars or planets

In one of the latest SCIFI movies, they collect a star absorving it entirely in a kind of planet size gun/machine. As mass cannot disappear, I assume it was just concentrated inside their machine (...
0
votes
0answers
18 views

How can I measure the stability of a many body gravitational system?

Suppose I have an N body planetary system interacting via gravity. Suppose I know the positions and momenta at t=0. How do I know if this system is stable (indefinitely)? By stable I mean the ...
0
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0answers
32 views

Heliocentric Cartesian position of moons

I have a working Kepler orbit system that is GPU accelerated to allow precision, speed and parallelism and more importantly allow as many factors as possible in calculation. For various reasons I ...
1
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1answer
50 views

Stability of the classical helium atom

Let us forget about quantum mechanics and confine ourselves to classical mechanics. The Hamiltonian for a classical helium atom would be $$ H = \frac{p_1^2 + p_2^2}{2m } - \frac{Z}{r_1} - \frac{Z}{...
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votes
3answers
112 views

Orbits for dummies [duplicate]

In a certain universe a perfectly spherical, uniformly dense planet is found to be in a stable orbit around a stable star. The rest of the universe is empty space with no silly stuff like dark matter. ...
1
vote
1answer
25 views

Would a celestial body in a horseshoe orbit be tidally locked to the planet?

A smaller celestial body like a moon or an asteroid can be in a horseshoe orbit around a planet. Since it might go inside the tidal lock radius (but does not stay inside it all the time), during the ...
1
vote
2answers
72 views

Which timestep should I use for a $N$-body simulation of the Solar system?

I am trying to implement a $N$-body simulation of the Solar system and I am stuck on the issue of the simulation timestep size. At first I would like to use a simple Euler stepping scheme. Knowing ...
2
votes
3answers
354 views

What would Earth have been without the Moon?

Would Earth rotation have been more slowed down because of the tidal effect from the Sun, as seems to be the case with Mercury and Venus? Due to the giant impact hypothesis the angular momentum from ...
1
vote
2answers
43 views

Reference frame, gravitation and kinetic energy

English is not my primary language. I apologize (and would like corrections) if the terms I use are not the right ones. In a geocentric reference frame, the moon rotates around the Earth. So its ...
0
votes
1answer
87 views

As planets orbit around the Sun, does the force of gravity due to the Sun remain constant?

I know that the force of gravity is: $$F = GMm/R^2$$ Where $G$ is gravitational constant, $M$ is mass of sun, $m$ is mass of the orbiting planet and $R$ is the distance between the center of their ...
3
votes
2answers
102 views

What is the zero of potential?

A satellite of mass $m$ is travelling at a speed $v_0$ in a circular orbit of radius $r_0$ around a fixed mass at $O$. Taking the zero of potential at $r=\infty$, show that the total energy of the ...
0
votes
3answers
84 views

Gravitational acceleration of asteroids [closed]

If an asteroid is moving through space at a speed that exceeds escape velocity of the earth and that asteroid is on a collision course with the earth will the asteroid Accelerate as it falls into the ...
16
votes
8answers
4k views

Why doesn't orbital body keep going faster and faster? [duplicate]

If we consider the change in velocity during an infinitesimal interval of an orbit: where body B is orbiting body A, we can see that the magnitude of the resultant vector (the green arrow) is ...
1
vote
2answers
352 views

Why Sun is not able to attract mercury closer?

As sun have a huge amount of attraction pull force , why its not able to pull tiny mercury? Is the whole solar system works in a push and pull network? Why bigger planets like earth, Saturn and ...
1
vote
2answers
59 views

What does “transfer” of angular momentum mean?

The Moon’s gravity produces tidal deformations or “bulges” in the Earth. Because of the Earth’s rotation, the line that goes through the bulges is not aligned with the line between the Earth and the ...
0
votes
0answers
30 views

Keplerian orbits and radial velocities: problem with true anomalies

I am writing a pure Python code to calculate radial velocities of stars with massive objects orbiting them. I am following the formalism from Murray & Correia (2011) (hereafter MC11). In a given ...
0
votes
1answer
32 views

Earth, Sun and beginner's reference frames

In the post-Newton era, where "absolute space" is not absolute, how is the reference frame in which "the Earth moves round the Sun" accurately defined?
1
vote
1answer
43 views

Energy diagram of a planet with fixed mechanical energy

Consider the following energy diagram for the motion of a planet about a star. The centrifugal potential curve can be represented once I fixed the angular momentum $\vec{L}$ of the planet. To fix the ...
0
votes
0answers
83 views

Celestial bodies trajectories relative to each other and with respect to the CM

In a two bodies $A$ and $B$ system, both under the action of an internal force of interaction $\vec{F}$, the motion of $A$ as seen from $B$, is equivalent to the motion of a single body of mass $\mu=\...
5
votes
1answer
68 views

Methods for handling close approaches in $N$-body simulations

In direct gravitational $N$-body simulations, what are the preferred methods for handling close approaches between bodies in order to preserve the accuracy of the evolution of the system?
1
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0answers
29 views

Can a satellite be put into orbit such that it will always remain directly over a city? [duplicate]

Isn't it possible if we just set it high enough so that it's angular speed matches with the earth's? I think that the city must be on the equator to make this happen. Am I correct? Please can anyone ...
0
votes
1answer
81 views

Can a satellite remain directly over a city?

Is it possible to put an artificial satellite into an orbit in such a way that it will always remain direct over a city (I mean at any specific place)?
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votes
3answers
557 views

How to learn celestial mechanics?

I'm a PhD student in math and am really excited about celestial mechanics. I was wondering if anyone could give me a roadmap for learning this subject. The amount of information about it on the ...
0
votes
0answers
23 views

Books on Celestial Mechanics [duplicate]

My background is mathematics. I would like to study celestial (not classical) mechanics and looking for an appropriate book. I found that somebody has already asked a similar question "How to learn ...
0
votes
0answers
20 views

Journals which publish articles on Celestial Mehanics [duplicate]

I'm from mathematics and want to study celestial mechanics further. In order to know literature at research level, I would like to know in which journals we can find papers on celestial mechanics. The ...
1
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0answers
17 views

Research groups in celestial mechanics [closed]

This Exchange may not be the right place to to ask this question, but I would like to know prominent research groups working in celestial mechanics. Although I'm interested in celestial mechanics, ...
0
votes
0answers
62 views

How to visualize gravity fields? [closed]

I'm creating a tool for intuitively prototyping routes through space. Part of this requires visualizing gravity. This is the formula for working at how much gravity is at a particular location: <...
0
votes
1answer
82 views

Newtonian Gravity Simulator?

Could anyone suggest me a good (and possibly free) Newtonian Gravity Simulator software available on the web, where it might be possible to simulate the Solar System dynamics and playing with it, by ...
2
votes
2answers
315 views

Planetary alignment of the gas giants?

There is this nice and new applet of the orbits of the planets around the sun: Solar System Orrery You can click and drag any planet and watch their relative orbits evolve in time. I was curious ...
0
votes
1answer
64 views

Can the constant $k$ from Kepler's third law be independent of the mass of the planet?

Consider Kepler's third law The square of the orbital period $\tau$ of a planet is directly proportional to the cube of the semi-major axis of its orbit $a$. $\frac{\tau^2}{a^3}=k$ The ...
5
votes
3answers
1k views

How would I calculate celestial body characteristics without a priori knowledge?

Without any a priori knowledge of the mass, speed, distance, and size of local celestial bodies (aside from Earth's size), what can I calculate and how from my "backyard" through observation? Edit: ...
1
vote
0answers
44 views

Semi-major axis , specific mechanical energy, its period and velocity at Apogee and Perigee and what the difference is [closed]

Hi im needing some help with two questions could you please show the formula and the way its solved?Thanks PS:Could you also explain what the difference of velocity and apogee and perigee? 1.)A ...
1
vote
1answer
37 views

Motion under gravitational forces

In a system of particles, can a particle be considered to be attracted to the combined center of mass of the other particles if the Newton's universal law of gravitation is used (the inverse square ...
1
vote
5answers
98 views

How can escape velocity and gravitational potential be higher in weaker gravitational fields?

on Earth we have an escape velocity of about 11180 m/s and a gravitational field of g=9.81 m/s^2. It would seem obvious that the escape velocity was higher for stronger gravitational fields. Often it ...
3
votes
3answers
81 views

Could the Earth-Moon rotation period equal one Earth year?

I just stumbled on this rather confused QA. The point seems to be if the Earth-Moon rotation period was identical to the Earth-year, then ... ... all three would stay in a line at all times. ...